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  1. MariaDB Server
  2. MDEV-30143

Segfault on select query using index for group-by and filesort

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    Description

      When I execute:

      SELECT T2.`Name` 
      FROM (
      	SELECT `Country` FROM `religion` GROUP BY `Country` ORDER BY COUNT(DISTINCT `Name`) DESC LIMIT 1 
      ) AS T1 
      INNER JOIN `country` AS T2
      ON T1.`Country`=T2.`Code`
      

      MariaDB crashes. The log is attached. A dump of the data is attached.

      Expected behaviour: The query returns country name with the highest count of distinct religions.

      Reproducibility: On macOS 12.6, case insensitive file system, with a fresh installation of MariaDB 10.7.3 from Homebrew I only get a misleading error message (the db remains responsive to other queries):

      2003 - Can't connect to MySQL server on '127.0.0.1' (61 "Connection refused")
      

      Severity: It causes a crash on a select query → marking as Critical.

      What I checked:

      1. I renamed `Country` column name to not clash with `country` table. It didn't have any impact.
      2. When I change `LIMIT 1` to `LIMIT 2`, the query works.

      Attachments

        1. Mondial.sql
          48 kB
        2. log.txt
          5 kB

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              oleg.smirnov Oleg Smirnov
              yzan Jan Motl
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              Dates

                Created:
                Updated:
                Resolved:

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